| Message ID | 675633f7ae9893371d35b238f06fd02a3acffebb.1697076650.git.gustavoars@kernel.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
| Series | clk: visconti: Fix undefined behavior bug and add bounds-checking coverage | expand |
On Wed, Oct 11, 2023 at 08:18:45PM -0600, Gustavo A. R. Silva wrote: > In order to gain the bounds-checking coverage that __counted_by provides > to flexible-array members at run-time via CONFIG_UBSAN_BOUNDS (for array > indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions), > we must make sure that the counter member, in this particular case `num`, > is updated before the first access to the flex-array member, in this > particular case array `hws`. See below: > > commit f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with > __counted_by") introduced `__counted_by` for `struct clk_hw_onecell_data` > together with changes to relocate some of assignments of counter `num` > before `hws` is accessed: > > include/linux/clk-provider.h: > 1380 struct clk_hw_onecell_data { > 1381 unsigned int num; > 1382 struct clk_hw *hws[] __counted_by(num); > 1383 }; > > However, this structure is used as a member in other structs, in this > case in `struct visconti_pll_provider`: > > drivers/clk/visconti/pll.h: > 16 struct visconti_pll_provider { > 17 void __iomem *reg_base; > 18 struct device_node *node; > 19 > 20 /* Must be last */ > 21 struct clk_hw_onecell_data clk_data; > 22 }; > > Hence, we need to move the assignments to `ctx->clk_data.num` after > allocation for `struct visconti_pll_provider` and before accessing the > flexible array `ctx->clk_data.hws`. And, as assignments for all members > in `struct visconti_pll_provider` are originally adjacent to each other, > relocate all assignments together, so we don't split up > `ctx->clk_data.hws = nr_plls` from the rest. :) > > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Looks good; thanks! Reviewed-by: Kees Cook <keescook@chromium.org>
Hi Gustavo A. R. Silva, Thanks for your patch! > -----Original Message----- > From: Gustavo A. R. Silva <gustavoars@kernel.org> > Sent: Thursday, October 12, 2023 11:19 AM > To: Michael Turquette <mturquette@baylibre.com>; Stephen Boyd > <sboyd@kernel.org>; iwamatsu nobuhiro(岩松 信洋 ○ＤＩＴＣ□ＤＩＴ○Ｏ > ＳＴ) <nobuhiro1.iwamatsu@toshiba.co.jp> > Cc: Kees Cook <keescook@chromium.org>; linux-clk@vger.kernel.org; > linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; Gustavo A. > R. Silva <gustavoars@kernel.org>; linux-hardening@vger.kernel.org > Subject: [PATCH 2/2][next] clk: visconti: Add bounds-checking coverage for > struct visconti_pll_provider > > In order to gain the bounds-checking coverage that __counted_by provides to > flexible-array members at run-time via CONFIG_UBSAN_BOUNDS (for array > indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family > functions), we must make sure that the counter member, in this particular case > `num`, is updated before the first access to the flex-array member, in this > particular case array `hws`. See below: > > commit f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with > __counted_by") introduced `__counted_by` for `struct clk_hw_onecell_data` > together with changes to relocate some of assignments of counter `num` > before `hws` is accessed: > > include/linux/clk-provider.h: > 1380 struct clk_hw_onecell_data { > 1381 unsigned int num; > 1382 struct clk_hw *hws[] __counted_by(num); > 1383 }; > > However, this structure is used as a member in other structs, in this case in > `struct visconti_pll_provider`: > > drivers/clk/visconti/pll.h: > 16 struct visconti_pll_provider { > 17 void __iomem *reg_base; > 18 struct device_node *node; > 19 > 20 /* Must be last */ > 21 struct clk_hw_onecell_data clk_data; > 22 }; > > Hence, we need to move the assignments to `ctx->clk_data.num` after > allocation for `struct visconti_pll_provider` and before accessing the flexible > array `ctx->clk_data.hws`. And, as assignments for all members in `struct > visconti_pll_provider` are originally adjacent to each other, relocate all > assignments together, so we don't split up `ctx->clk_data.hws = nr_plls` from > the rest. :) > > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Acked-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Best regards, Nobuhiro
diff --git a/drivers/clk/visconti/pll.c b/drivers/clk/visconti/pll.c index 1f3234f22667..e9cd80e085dc 100644 --- a/drivers/clk/visconti/pll.c +++ b/drivers/clk/visconti/pll.c @@ -329,12 +329,12 @@ struct visconti_pll_provider * __init visconti_init_pll(struct device_node *np, if (!ctx) return ERR_PTR(-ENOMEM); - for (i = 0; i < nr_plls; ++i) - ctx->clk_data.hws[i] = ERR_PTR(-ENOENT); - ctx->node = np; ctx->reg_base = base; ctx->clk_data.num = nr_plls; + for (i = 0; i < nr_plls; ++i) + ctx->clk_data.hws[i] = ERR_PTR(-ENOENT); + return ctx; }
In order to gain the bounds-checking coverage that __counted_by provides to flexible-array members at run-time via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions), we must make sure that the counter member, in this particular case `num`, is updated before the first access to the flex-array member, in this particular case array `hws`. See below: commit f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with __counted_by") introduced `__counted_by` for `struct clk_hw_onecell_data` together with changes to relocate some of assignments of counter `num` before `hws` is accessed: include/linux/clk-provider.h: 1380 struct clk_hw_onecell_data { 1381 unsigned int num; 1382 struct clk_hw *hws[] __counted_by(num); 1383 }; However, this structure is used as a member in other structs, in this case in `struct visconti_pll_provider`: drivers/clk/visconti/pll.h: 16 struct visconti_pll_provider { 17 void __iomem *reg_base; 18 struct device_node *node; 19 20 /* Must be last */ 21 struct clk_hw_onecell_data clk_data; 22 }; Hence, we need to move the assignments to `ctx->clk_data.num` after allocation for `struct visconti_pll_provider` and before accessing the flexible array `ctx->clk_data.hws`. And, as assignments for all members in `struct visconti_pll_provider` are originally adjacent to each other, relocate all assignments together, so we don't split up `ctx->clk_data.hws = nr_plls` from the rest. :) Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> --- drivers/clk/visconti/pll.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)